Some type of variables are not safely copied by Script.Clone.

[matszpk]

My experiments with Script.Clone method give unexpected results. After cloning Compiled object, the global map and arrays values has been copied to origin Compiled object. Your code doesn't make new copy array values and map values, just simply copy globals array and your code of Clone doesn't make safe copy of Compiled object. Global mutable maps and arrays should be copied deeply to make safe-concurrent copy of state.

[misiek08]

@matszpk can you provide simplest example or an test to show this behavior? This will be close to fixing so even patch is welcome :)

[ipsusila]

First of all, thank you for the great works and contributions in Tengo.
I just start experimenting with Tengo and found this issue. I think the following example script shows what @matszpk means.

// A script with two global variables assigned by host
// 1. `round` an integer type
// 2. `data` a map type

// 1. overwrite primitive type, safe
round = 1000

last_key := ""
for key, val in data {
    last_key = key
}
// 2. delete an entry from data (map type) is not safe in `cloned` bytecode
// the value in original compiled bytecode is being modified
delete(data, last_key)

I verified the behaviour, and propose a patch at ipsusila@14bfd45.

[geseq]

@ipsusila can you create a PR please